Voltage regulator



Nov. 24, 1959 s. T. KOHN 2,914,721

VOLTAGE REGULATOR Filed Sept. 23, 1958 A. c. I

SUPPLY SAMUEL T. KOHN INVENTOR ATTORNEY United States Patent VOLTAGE REGULATOR Application September 23, 1958, Serial No. 762,832

6 Claims. (Cl. 323-60) This invention relates to a voltage regulator which employs resonance as one ofthe features of regulation. It includes a single saturable-core. and'is arranged for stabilizing an alternating current voltage derived from an alternating current power supply.

Voltage regulators employing resonant circuits and saturable core reactors have been designed in many forms employing many combinations of primary and secondary windings. Such regulators havebeen very popular because they have no moving parts, no rectifiers, and no heater elements. They are self-contained and last for a long time without servicing. The present invention differs from prior voltage regulators of this general type in that it has a combination of windings which enclose single legs of the core and one control winding which encloses two legs of the core.

One of the objects of this invention is to provide an improved voltage regulator which avoids one or more of the disadvantages and limitations of prior art regulators.

Another object of the invention is to provide a voltage regulator which is low in cost and which provides good regulation within a wide range of applied voltage and load.

Another object of the invention is to reduce the weight of voltage regulators in proportion of electrical power provided at the output terminals.

T he invention comprises a single saturable core having a primary circuit which includes input terminals, a first primary winding on one of the core legs and a secondary primary winding which is wound around both legs of the core material. The secondary circuit includes a first secondary winding mounted adjacent to the first primary winding, a second secondary winding mounted on a core leg opposite to the core leg which holds the first primary winding, these two windings being substantially in series connection with a pair of output terminals. A capacitor is connected across the second secondary winding for resonance at the frequency of the applied voltage.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawing.

The figure is a schematic diagram of connections of the voltage regulator.

The voltage regulator includes a closed core 10 of oblong shape having two legs 10A and 10B which are considerably longer than the other legs 10C and 10D. One form of the core 10 which gives good results has a ratio of two to one of the longer to shorter legs. This ratio, however, is not critical and other core forms may be used. All the windings are carried by the longer legs 10A and 10B, these windings including a first primary winding 11 having one end connected to an input terminal 12, and a second primary winding 13 having one end connected to the other input terminal .14. The two primary windings are in series. The first primary winding encloses only one leg 10A while the second primary winding 13 encloses both of the longer legs 10A and 108. The windings are arranged so that they aid in producing additive magneto motive forces in leg 10A but oppose each other in leg 10B.

The device includes two secondary windings, a first sec- 2,914,721 Patented Nov. 24, 1959 ondary winding 15 enclosing 'leg' loA and a second secondary winding enclosing leg 10B. The first secondary winding 15 is connected between an output terminal 17 and a tap 18 on the second secondary winding 16. The second secondary winding has its one end connected to an output terminal 20 and a capacitor 21 is connected across the entire winding. The output terminals are connected to a load 22 which may vary over a wide range of impedance values.

When a normal voltage is applied at input terminals 12 and 14 and an average load is connected to terminals 17 and 14, the first primary winding 11 sends flux in the direction shown by the arrow aided by the left part of the second primary winding 13. Windings 15 and the right side of winding 13 oppose this flux but their magneto motive forces are not strong enough to overcome the flux generated by winding 11. This main flux induces a voltage in output winding 16 which, aided by resonance, produces an output voltage at terminals 17 and 20. Secondary Winding 15 produces a small voltage which is in opposition to the voltage produced by winding 16 but for normal loads this opposing voltage has little effect.

When the input voltage is increased above its normal value, the current and flux both tend to increase in the primary windings, thereby increasing the saturation of the core. A larger voltage is generated in winding 16 but the saturation of the core reduces the inductance of winding 16 and changes the resonant frequency of the resonant combination 16, 21. This action lowers the output voltage and reduces it to a value which is close to normal. The increase in current and resultant increase in flux also increases the induced voltage in Winding 15 and since this is in opposition to the voltage produced by winding 16 the result is a still lower output voltage. The increase in current in winding 13 causes the magnetomotive forces set up by the two halves of this winding to increase, thereby causing increased stray fields and again lowering the output voltage. The result of all these actions is an output voltage which is substantially equivalent to the desired regulated value. A lowering of the input voltage produces effects which are the reverse of the eifects described above.

When the output load is lowered, thereby increasing the current drawn from windings 16 and 15 and acting to reduce the output voltage, the back magnetomotive force of Winding 16 is increased, thereby reducing the total flux in the core and reducing the saturation. Reducing the saturation increases the inductance of winding 16, thereby reducing the resonant frequency of the resonant circuit 16, 21, to a value which is closer to the applied frequency and thereby increasing the output voltage to a value which is close to the desired value. The small voltage generated by winding 15 is increased due to this action and aids in the regulating action by lowering the core saturation and further increasing the inductance of winding 16. The stray field is increased as before. The re sult of these actions is a change in the resonant frequency of the resonant circuit 16, 21, which substantially compensates for the change in output voltage and retains it at the desired value.

One practical example of a voltage regulator made in conformity with the above description included the following characteristics.

The foregoing disclosure and drawing are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims.

I claim:

1. A voltage regulator comprising, a pair of input terminals for connection to a source of alternating current power, a pair of output terminals for connection to a load, a single saturable core having at least twolegs, a first primary Winding on one of the core legs, a second primary winding in series with the first and said pair of input terminals, said second primary winding enclosing both of said legs, a first secondary winding mounted on one of the core legs, a second secondary winding mounted on one of the core legs and shunted by a capacitor, said first secondary windingconnected between one of said output terminals and a tap on the seocnd secondary winding, and a connection between one side of said secondary winding and the other output terminal.

2. A voltage. regulator comprising, a pair of input terminals for connection to a source of alternating current power, a pair of output terminals for connection to a load, a single saturable core having two legs, a first primary winding on one of the core legs, a second primary winding in series with the first and said pair of input terminals, said second winding enclosing both of said legs for generating opposing magnetomotive forces in the core and thereby causing stray magnetic flux, a first secondary winding mounted on one of the core legs, a second secondary winding mounted on one of the core legs and shunted by a capacitor, said first secondary winding connected between one of said output terminals and a tap on the second secondary winding, and a connection between one side of said second secondary winding and the other output terminal;

3. A voltage regulator comprising, a pair of input terminals for connection to a source of alternating current power, a pair of output terminals for connection to a load, a single closed: saturable core having two parallel legs, a first primary winding on one of the core legs, a second primary winding in series with the first and said pair of input terminals, said second primary winding enclosing both of said legs for generating opposing magnetomotivc forces in the core and thereby causing stray magnetic flux, afirst secondary winding, mounted on the core adjacent to the first primary winding, a second secondary winding mounted on a core leg opposite to the leg. which holdsthe, first primaryv winding, said secondary winding shunted'by a capacitor, said first secondary winding. connected betweenlone ofs-saidoutput terminals and a tap on the'second secondary Winding, and a-connection between one side of said second secondary winding and:

the other. output terminal.

4. A voltage regulator asset forth in' claim 3 wherein said second secondary winding and said capacitor form a resonant circuit at no load at the frequency of the input power.

5. A voltage regulator as set forth in claim 3 wherein said first primary winding has a number of turns sufficient to produce a magnetomotive force substantially greater than that produced by the second primary winding.

6. A voltage regulator as set forth in claim 3 wherein said second primary winding increases the amount of stray flux responsive to the current flowing in the winding.

No references cited.

I I-m. 

